Driving the news: Last month, a ballistic missile attack on UAE-backed Security Belt Forces in the interim capital of Aden killed more than 30 soldiers. Although Houthis claimed responsibility, the STC accused government officials from the al-Islah party, which is loosely affiliated with the Muslim Brotherhood, of plotting the attack to weaken their southern leadership.

• STC forces subsequently overtook Aden's airport and advanced to nearby cities of Shabwa and Abyan, while the government mobilized troops from northern and tribal areas — renewing a sense of oppression that augmented calls for southern independence.
• Tensions escalated further after the UAE conducted an airstrike against targets it declared terrorists but which the Yemeni government claimed as members of its army.

Context: The southern independence movement has been a 2-decade-long struggle, slowed by state repression and imprisonment of its leaders.

• Yemen's government has been self-exiled in Riyadh, unable to provide security for citizens or fully function in the south, which diminished its support.
• As the Yemen government's relationship with the UAE has soured, it has asked its Saudi partners to help end the Emiratis' “flagrant interference” on behalf of the STC.

What to watch: Since STC-allied forces have assisted the Saudi-led military coalition, they hope to secure guarantees for their overall objective of reclaiming their southern state — support the Saudis are unlikely to deliver.

• At most, Saudi Arabia might back a power-sharing agreement, not wanting to harm its relationship with Yemen's government or risk being left with a de facto Houthi state on the Saudi border.
• The fraught politics of the conflict may continue to limit open dialogue, complicating attempts to accommodate each party's divergent interests.

Fatima Abo Alasrar is a non-resident scholar at the Middle East Institute.

The big picture: A source tells Reuters that the UAE wants to establish itself as the more mature player in the region, especially as Saudi foreign policy grows increasingly "impulsive and interventionist" under Crown Prince Mohammed bin Salman (MBS).

• In Washington, where the UAE has an extensive lobbying operation, the country has also sought to distance itself from MBS after the murder of journalist Jamal Khashoggi enraged U.S. lawmakers.
• "The UAE wants to be seen as the small country that facilitates peace and stability rather than an appendage to a triumphant expansionist Saudi," the source said.

Why it matters: If the alliance is indeed fracturing, it could have huge reverberations in the Middle East, especially in relation to the Israeli-Palestinian peace process and the Trump administration's "maximum pressure" campaign against Iran.